In recent years, an interference-type optical scanning observation apparatus which can create a tomographic image of a subject using low-coherence light for diagnosis of body tissue has been proposed, for example in Japanese Unexamined Patent Application Publication No. 11-148897.
With this conventional example, a detachable optical scanning probe is used to obtain a tomographic image of body tissue.
In the event of mounting a detachable optical scanning probe on an apparatus at a low-coherence light source side, the interference system must be adjusted since an image with an offset focal point will be obtained otherwise, so optical capabilities must be set in a suitable state such as allowing detection of interference light at the focal position, and so forth.
Also, in recent years, an optical tomographic imaging apparatus capable of obtaining optical information within the tissue for diagnosing body tissue has been proposed, besides an imaging apparatus for obtaining optical information of the surface state of the tissue.
Japanese Unexamined Patent Application Publication No. 2000-126115 discloses an optical scanning probe apparatus. A probe which has optical scanning means at the tip of the probe, and is capable of variation in the focal position in the depth-wise direction, so as to obtain an observation image along the depth-wise direction, is disclosed in this Japanese Unexamined Patent Application Publication No. 2000-126115.
Also, PCT Japanese Translation Patent Publication No. 6-511312 (corresponding to U.S. Pat. No. 5,321,501) discloses a technique for Optical Coherence Tomography (OCT) whereby a tomography image in the depth-wise direction of the body can be obtained using low-coherence interferometry.
Further, Japanese Unexamined Patent Application Publication No. 11-72431 (corresponding to U.S. Pat. No. 6,069,698) discloses an optical tomographic imaging apparatus capable of obtaining high-resolution optical tomographic images by combining the optical probe disclosed in Japanese Unexamined Patent Application Publication No. 2000-126115 with low-coherence interferometry.
However, with the preceding example, techniques for setting the optical capabilities to a suitable state are not disclosed.
Also, even in the event that the optical scanning probe is not detachable, an arrangement wherein optical capabilities can be set to a suitable state is desirable, for cases wherein the optical path length and the like of the light transmitting system changes due to change in temperature, and so forth.
Also, setting to a suitable optical property state for cases wherein the focal depth of the optical system for converging at the tip side of the scanning probe is shallow is also desired.
However, the probe disclosed in Japanese Unexamined Patent Application Publication No. 2000-126115 includes a focal point variation mechanism using a piezoelectric device in order to change the position of the focal point in the depth-wise direction, but the size of the focal point variation mechanism is large. Accordingly, the length of the hard portion at the tip of the probe becomes long, creating the problem that scanning and positioning within the body become difficult.
Also, FIG. 15 in Japanese Unexamined Patent Application Publication No. 2000-126115 discloses a method for varying the focal point using push-pull rods. However, this method cannot be realized with flexible and long probes which can be inserted through or built into endoscopes.
Further, Japanese Unexamined Patent Application Publication No. 2000-126115 discloses an embodiment for advancing and retreating a contacting member with the subject, as a focal position variation mechanism. However, this embodiment requires force of an amount for moving the subject or the probe itself, so the size of the actuator becomes great, producing the problem that the apparatus cannot be readily reduced in size. Also, force is applied to the subject itself, which is soft in nature, so there is the problem that fine positional control is difficult.
Moreover, an embodiment is also disclosed wherein only the converging means are advanced and retreated, but in the event of combining and using with low-coherence interference, there is the problem that the detection position from low-coherence interference and the converging position are offset, markedly deteriorating the detecting efficiency.
Also, Japanese Unexamined Patent Application Publication No. 2000-126115 discloses arrangements for advancing and retreating a contacting member with the subject, or advancing and retreating the converging means, as focal point moving variation mechanisms, but this requires moving objects with large load or mass, so changing the focal position quickly has been difficult.
Japanese Unexamined Patent Application Publication No. 11-72431 discloses an apparatus combining low-coherence light interference and a high-resolution optical system using a micro-optical scanner. This also discloses a configuration for oscillating a scan head having a micro-optical scanner, so as to scan the converging position in the depth-wise direction. However, there is the problem in combining with low-coherence interference in that the detection position from low-coherence interference and the converging position are offset, markedly deteriorating the detecting efficiency.
Accordingly, the present invention has been made in light of the above-described points, and it is an object thereof to provide an optical scanning observation apparatus and a setting method thereof capable of readily setting to a state wherein optical capabilities are suitable.
Also, it is an object of the present invention to provide an optical scanning observation apparatus wherein the tip hard portion is short, and has a focal point variation mechanism capable of precise control.
Further, it is an object of the present invention to provide an optical scanning observation apparatus capable of quick focal position variation.
Moreover, it is an object of the present invention to provide an optical scanning observation apparatus wherein the detection position from low-coherence interference accords with the converging position even if the focal position is varied, in combination with low-coherence interference.